Molds with coatings for high temperature use in shaping glass-based material

ABSTRACT

A mold with a multi-layer coating is disclosed. The mold may include a mold body having an outer surface and a multi-layer coating disposed on the outer surface. The multi-layer coating may include a diffusion barrier layer disposed on the outer surface of the mold body and an intermetallic layer disposed on the diffusion barrier layer, wherein the intermetallic layer comprises Ti, Al, and an additional metal selected from the group consisting of Zr, Ta, Nb, Y, Mo, Hf, and combinations thereof The diffusion barrier layer may restrict diffusion of metal from the mold body to the intermetallic layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 U.S.C. §119 ofU.S. Provisional Application Ser. No. 62/280885 filed on Jan. 20, 2016,the content of which is relied upon and incorporated herein by referencein its entirety.

BACKGROUND

Field

The present specification generally relates to molds for shapingglass-based material and, more specifically, molds having coatings forhigh temperature use in shaping glass-based material.

Technical Background

Glass articles can be formed into 3D shapes by heating the glass to avisco-elastic state and contacting the glass with a mold. However,forming three-dimensionally shaped glass articles with high softeningpoint glass compositions, such as alkali aluminosilicate glasscompositions, can be challenging. For example, some glass compositionshave high softening points (sometimes greater than 900° C.), which makesa precision molding process more difficult since the glass needs to beheated to higher temperatures in order to reach a visco-elastic statesuitable to forming. Additionally, some glass compositions have highpercentages of sodium (such as, for example, greater than 10 mol %).Sodium may be highly mobile and reactive at high temperatures.Contacting a mold surface with sodium at high temperature may degradethe mold surface and, subsequently, the quality of the molded glass.Furthermore, pitting in the glass may be caused by particulatecontaminants, such as contaminants from the mold. Pitting may also becaused by glass sticking to the mold surface where the glass to moldbond strength exceeds the strength of glass, creating divots in theglass due to so called “pullouts”. Other cosmetic defects such as stainsand/or scuffing may be observed on 3D molded glass surfaces, especiallywhen using high forming temperatures and longer contact times.

Accordingly, a need exists for molds with coatings that are compatiblewith high temperatures when shaping glass-based material.

SUMMARY

In a first aspect a mold includes a mold body having an outer surfaceand a multi-layer coating disposed on the outer surface. The multi-layercoating includes a diffusion barrier layer disposed on the outer surfaceof the mold body and an intermetallic layer disposed on the diffusionbarrier layer, wherein the intermetallic layer comprises Ti, Al, and anadditional metal selected from the group consisting of Zr, Ta, Nb, Y,Mo, Hf, and combinations thereof. The diffusion barrier layer restrictsdiffusion of metal from the mold body to the intermetallic layer.

In a second aspect according to the first aspect, the multi-layercoating also includes a transition layer disposed between the diffusionbarrier layer and the intermetallic layer, wherein the transition layercomprises a change in nitrogen content with a higher molar nitrogencontent in a portion of the transition layer closest to the diffusionbarrier layer and a lower molar nitrogen content in a portion of thetransition layer closest to the intermetallic layer.

In a third aspect according to any preceeding aspect, the intermetalliclayer comprises a change in the additional metal content with a lowermolar content of the additional metal in a portion of the intermetalliclayer closest to the diffusion barrier layer and a higher molar contentof the additional metal in a portion of the intermetallic layer farthestfrom the diffusion barrier layer.

In a fourth aspect according to any preceeding aspect, the multi-layercoating also includes an oxidized intermetallic layer disposed on theintermetallic layer.

In a fifth aspect according to any preceeding aspect, the ratio oftitanium molar content to aluminum molar content in the multi-layercoating is in a range from about 0.67 to about 1.

In a sixth aspect according to any one of the first through fourthaspects, the ratio of titanium molar content to aluminum molar contentin the multi-layer coating is about 1.

In a seventh aspect according to any one of the first through fourthaspects, the ratio of titanium molar content to aluminum molar contentin the multi-layer coating is greater than or equal to about 0.67 andless than about 1.

In an eighth aspect according to any preceeding aspect, a sum of themolar concentration of titanium and aluminum in the intermetallic layeris greater than or equal to the molar concentration of the additionalmetal in the intermetallic layer.

In a ninth aspect according to any one of the first through seventhaspects, the sum of the molar concentration of titanium and aluminum inthe intermetallic layer is less than the molar concentration of theadditional metal in the intermetallic layer.

In a tenth aspect according to any preceeding aspect, the multi-layercoating also includes a metal layer comprising the additional metal ofthe intermetallic layer disposed on the intermetallic layer.

In an eleventh aspect according to the tenth aspect, the intermetalliclayer comprises a change in additional metal content with a lower molarcontent of the additional metal in a portion of the intermetallic layerclosest to the diffusion barrier layer and a higher molar content of theadditional metal in a portion of the intermetallic layer closest to themetal layer.

In a twelfth aspect according to the tenth or eleventh aspect, themulti-layer coating also includes an oxidized metal layer disposed onthe metal layer.

In a thirteenth aspect according to any preceeding aspect, theadditional metal is zirconium.

In a fourteenth aspect according to any preceeding aspect, the mold bodyis predominantly a metal selected from the group consisting of iron,nickel, chromium, copper, mixtures thereof, and alloys thereof.

Additional features and advantages of the embodiments described hereinwill be set forth in the detailed description which follows, and in partwill be readily apparent to those skilled in the art from thatdescription or recognized by practicing the embodiments describedherein, including the detailed description which follows, the claims, aswell as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description describe various embodiments and areintended to provide an overview or framework for understanding thenature and character of the claimed subject matter. The accompanyingdrawings are included to provide a further understanding of the variousembodiments, and are incorporated into and constitute a part of thisspecification. The drawings illustrate the various embodiments describedherein, and together with the description serve to explain theprinciples and operations of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

Below is a brief description of the drawings. It is noted that thedrawings are not to scale and are not intended to provide a comparisonof the relative sizes of the various layers depicted in the drawings.

FIG. 1 schematically depicts a cross sectional diagram of a multi-layercoating on a mold body, according to one or more embodiments shown anddescribed herein;

FIG. 2. schematically depicts a cross sectional diagram of a multi-layercoating on a mold body, according to one or more embodiments shown anddescribed herein;

FIG. 3 schematically depicts a cross sectional diagram of a multi-layercoating on a mold body, according to one or more embodiments shown anddescribed herein;

FIGS. 4A-4C schematically depict a cross sectional diagram of amulti-layer coating on a mold body, according to one or more embodimentsshown and described herein;

FIGS. 5A-5F schematically depict a cross sectional diagram of amulti-layer coating on a mold body, according to one or more embodimentsshown and described herein;

FIG. 6 is a plot of the atomic weight percentage vs. the depth of acoated mold for each element;

FIG. 7 is plot comparing the surface roughness of a glass sheet shapedwith different molds;

FIG. 8 is the exemplary thermal and vacuum profile of the glass and moldwhen shaping the glass on an nickel 201 mold discussed in Example 2; and

FIG. 9 is the exemplary thermal and vacuum profile of the glass and moldwhen shaping the glass on an Inconel 600 mold discussed in Example 2

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of moldshaving coatings for use in shaping glass-based materials, examples ofwhich are illustrated in the accompanying drawings. Whenever possible,the same reference numerals will be used throughout the drawings torefer to the same or like parts.

The following description is provided as an enabling teaching. To thisend, those skilled in the relevant art will recognize and appreciatethat many changes can be made to the various embodiments describedherein, while still obtaining the beneficial results. It will also beapparent that some of the desired benefits can be obtained by selectingsome of the features without utilizing other features. Accordingly,those who work in the art will recognize that many modifications andadaptations to the present embodiments are possible and can even bedesirable in certain circumstances and are a part of the presentdescription. Thus, the following description is provided as illustrativeand should not be construed as limiting.

In this specification and in the claims which follow, reference will bemade to a number of terms which shall be defined to have the meaningsdetailed herein.

The term “about” references all terms in the range unless otherwisestated. For example, about 1, 2, or 3 is equivalent to about 1, about 2,or about 3, and further comprises from about 1-3, from about 1-2, andfrom about 2-3. Specific and preferred values disclosed forcompositions, components, ingredients, additives, and like aspects, andranges thereof, are for illustration only; they do not exclude otherdefined values or other values within defined ranges. The compositionsand methods of the disclosure include those having any value or anycombination of the values, specific values, more specific values, andpreferred values described herein.

The indefinite article “a” or “an” and its corresponding definitearticle “the” as used herein means at least one, or one or more, unlessspecified otherwise

As used herein, the term “glass-based” includes glass and glass-ceramicmaterials.

As used herein, the term “substrate” describes a glass-based sheet thatmay be formed into a three-dimensional structure.

Generally, disclosed herein are molds with a multi-layer coating for usein shaping glass-based materials. The molds may be used to shape asubstantially flat glass-based substrate or sheet into athree-dimensional glass-based article. In some embodiments the mold mayinclude a mold body having a surface and a multi-layer coating disposedon at least a portion of the outer surface. The surface of the mold bodymay have a three-dimensional surface profile corresponding to a desiredthree-dimensional shape for a glass-based article which is shapedagainst the mold. In some embodiments, more than one mold body may beutilized to form a glass-based article. For example, two mold bodies maymake contact with opposite sides of a glass-based material. Accordingly,in a two-mold embodiment, each mold body may have a multi-layer coatingdisposed thereon. The multi-layer coatings described herein may increasethe temperature resistance of the mold, provide a surface that reducesstickiness to the glass-based material, decrease surface roughness tominimize or prevent imprinting pits onto the glass-based material,providing wear resistance to scuffing, and/or increasing the life of themold by preserving the underlying mold surface so that the mold coatingto be stripped and recoated multiple times before the mold surface mustbe re-machined.

FIG. 1 depicts a partial cross-section view of an exemplary mold 100having a mold body 110 with a surface 112 and a multi-layer coating 120disposed on at least a portion of surface 112. For simplicity thepartial cross-sectional view of mold 100 in FIG. 1 illustrates a flatportion of surface 112 of mold body 110. However, as noted above surface112 of mold body 110 may have a three-dimensional surface profilecorresponding to a desired three-dimensional shape for a glass-basedarticle which is shaped against mold 100.

Mold 100 may be any suitable mold capable of shaping molten glass.Examples of molds include, but are not limited to, tools such as dies,or other manufacturing presses. Mold body 110 may include any metal orother material capable of withstanding high temperatures (for example,760° C. to 900° C.), such as refractory metals, refractory ceramics, orthe like. In some embodiments, mold body 110 may include any metal orother material with a high hardness, for example a Rockwell hardness ofgreater than 65B. A high hardness may reduce scuffing or abrading of themold body from glass-based material over time and/or may provideresistance to glass chips or other contaminants embedding in the moldbody, which could cause imprints on the surface of the shapedglass-based materials. In some embodiments mold body 110 may be a metalincluding, but not limited to, iron, nickel, chromium, and copper, aswell as mixtures thereof and alloys thereof. In some embodiments,surface 112 of mold body 110 may predominantly include a metal selectedfrom the group consisting of iron, nickel, chromium, copper, mixturesthereof, and alloys thereof As used herein, “predominantly” means ametal, metal mixture or metal alloy wherein metals from the above groupmake up more than 50% by weight of the metal, mixture, or alloy.Illustrative examples include, but are not limited to, cast iron, steelsor steel alloys such as H13, S7 and P20, stainless steels 309, 310 and420, and nickel alloys such as Hastelloy® alloys (for example,Hastelloy® 214) and Inconel® alloys (for example, Inconel® 718 orInconel® 600).

In some embodiments, multi-layer coating 120 may include a diffusionbarrier layer 122 disposed on surface 112 of mold body 110 and anintermetallic layer 124 disposed on diffusion barrier layer 122. As usedherein, the term “dispose” includes coating, depositing and/or forming amaterial onto a surface using any known method in the art. The phrase“disposed on” includes the instance of forming a material onto a surfacesuch that the material is in direct contact with the surface and alsoincludes the instance where the material is formed on a surface, withone or more intervening material(s) between the disposed material andthe surface.

In some embodiments, diffusion barrier layer 122 may include a nitride,such as TiAlN, TiAlSiN, TiN, AlN, TiAlXN (where X may include a metalsuch as, but not limited to Nb, Zr, Y, Mo, or Hf) or combinationsthereof. In some embodiments, diffusion barrier layer 122 may have amolar nitrogen content of greater than about 30%. The molar nitrogencontent may be measured using an electron microprobe or using X-rayphotoelectron spectrometry (XPS). Diffusion barrier layer 122 mayrestrict diffusion of metals from the mold body 110 to an outermostlayer of the multi-layer coating. As noted herein, metals from the moldbody 110, such as Ni or Cr, may be mobile at elevated temperatures, andtheir presence in the outermost layer of the multi-layer coating maycause defects, such as pitting. Additionally, diffusion barrier layer122 may also restrict diffusion of glass materials that transfer to theoutermost layer of mold 100 during shaping of a glass-based materialfrom an outermost layer of mold 100 to mold body 110. Some glassmaterials, such as sodium, may cause corrosion in the material of themold body 110. As the diffusion barrier layer 122 prevents and/orminimizes the diffusion of these species, the diffusion barrier layer122 also prevents and/or minimizes defects caused by such species.

The diffusion barrier layer 122 may also prevent and/or minimize theformation of voids in the mold body 110 that are due to the outdiffusionof base metals into the multi-layer coating. Specifically, the diffusionbarrier layer 122 prevents and/or minimizes the diffusion of base metalsinto or through the remainder of the multi-layer coating and, as aresult, mitigates the formation of voids in the mold body 110 that areleft by out-diffused metal. Since voids may form with less severityand/or frequency with a diffusion barrier layer 122, the diffusionbarrier layer 122 may enable repeat stripping and recoating of molds,and extends the service life of the mold. In some embodiments, diffusionbarrier layer 122 may have a thickness in a range from about 25 nm toabout 2,000 nm, from about 100 nm to about 600 nm, from about 300 nm toabout 500 nm, or from about 1,000 nm to about 2,000 nm.

In some embodiments, intermetallic layer 124 may include Ti, Al, and anadditional metal selected from the group consisting of Zr, Ta, Nb, Y,Mo, Hf, and combinations thereof. As used herein, the term“intermetallic” means a material composed of two or more types of metalatoms, which exist as homogeneous, composite substances and differdiscontinuously in structure from that of the constituent metals. Theadditional metal, which may be a refractory metal, may be included inintermetallic layer 124 because it may be less reactive with theglass-based materials that are shaped against the mold, and therefore,reduces sticking of the glass-based materials to the mold during shapingand provides a shaped glass-based material with better surfacecosmetics. Also, the additional metal, which may be a refractory metal,may be included in intermetallic layer 124 because it may make themulti-layer coating more resistant to damage from high temperatures (forexample, 760° C. to 900° C.), which the mold may need to withstand whenforming glass-based materials having softening points at hightemperatures.

In some embodiments the composition of intermetallic layer 124 may bemodified based on the temperature is must withstand based on thesoftening point of the glass-based material to be shaped against themold. Modification of the composition of intermetallic layer 124 mayinclude modifying the weight percentage of the additional metal, theratio of the molar concentration of Ti to the molar concentration of Al,and/or the relationship between the sum of the molar concentration oftitanium and aluminum in the intermetallic layer and the molarconcentration of the additional metal in the intermetallic layer. Insome embodiments, intermetallic layer 124 may include the additionalmetal in a range from about 20 wt % to about 40 wt %, about 20 wt % toabout 35 wt %, about 20 wt % to about 30 wt %, about 25 wt % to about 40wt %, about 25 wt % to about 35 wt %, about 25 wt % to about 30 wt %,about 30 wt % to about 40 wt %, about 30 wt % to about 35 wt %, or about35 wt % to about 40 wt %. The weight percentage may be measured using anelectron microprobe, XPS, or secondary-ion mass spectroscopy (SIMS). Insome embodiments, the ratio of the molar concentration of Ti to themolar concentration of Al in intermetallic layer 124 may be in a rangefrom about 0.67 to about 1, in a range from about 0.67 to less thanabout 1, about 1, or greater than about 1. In some embodiments, themolar concentration of Al is lowered to reduce the reactivity of theintermetallic layer with the glass-based material that is shaped againstthe mold and the likelihood that the glass-based material that is shapedagainst the mold will stick to the mold. Depending on the composition ofthe glass-based material that is shaped against the mold, the ratio ofthe molar concentration of Ti to the molar concentration of Al inintermetallic layer 124 may be greater than 1 to increase thetemperature the multi-layer coating can withstand. In some embodiments,the multi-layer coating may withstand temperatures of up to about 800°C. when the ratio of the molar concentration of Ti to the molarconcentration of Al is in a range from about 0.67 to less than about 1.In some embodiments, the multi-layer coating may withstand temperaturesof up to about 850° C. when the ratio of the molar concentration of Tito the molar concentration of Al is about 1. In some embodiments, thesum of the molar concentrations of Ti and Al may be greater than orequal to the molar concentration of Zr. In some embodiments, the sum ofthe molar concentrations of Ti and Al may be greater than or equal tothe molar concentration of Zr. The molar concentration of the elementsmay be measured using an electron microprobe or XPS.

In some embodiments, intermetallic layer 124 may be a gradient layerwherein the amount of additional metal and/or the amount of Ti and Alchanges through the thickness of the layer. In some embodiments,intermetallic layer 124 may have a change in the additional metalcontent with a lower molar content of the additional metal in a portionof the intermetallic layer closest to diffusion barrier layer 122 and ahigher molar content of the additional metal in a portion of theintermetallic layer farthest from diffusion barrier layer 122. In someembodiments, the change in the additional metal content may changecontinuously through the thickness of intermetallic layer 124. In someembodiments, the change in additional metal content may changediscontinuously through the thickness of intermetallic layer 124. Thechange in the amount of additional metal may be useful when there is adifference in the coefficient of thermal expansion (CTE) betweendiffusion barrier layer 122 and the additional metal of intermetalliclayer 124. In some embodiments, intermetallic layer 124 may have achange in Ti and Al content with a higher molar Ti and Al content in aportion of the intermetallic layer closest to diffusion barrier layer122 and a lower molar Ti and Al content in a portion of theintermetallic layer farthest from diffusion barrier layer 122. In someembodiments, the change in Ti and Al content may change continuouslythrough the thickness of intermetallic layer 124. In some embodiments,the change in Ti and Al content may change discontinuously through thethickness of intermetallic layer 124. In some embodiments, intermetalliclayer 124 may have a thickness in a range from about 25 nm to about2,000 nm, from about 100 nm to about 600 nm, from about 300 nm to about500 nm, or from about 1,000 nm to about 2,000 nm.

In some embodiments, as shown for example in FIG. 2, a multi-layercoating 220 may include a transition layer 223 between diffusion barrierlayer 122 and intermetallic layer 124 such that diffusion barrier layer122 may be disposed on mold body 110, transition layer 223 may bedisposed on diffusion barrier layer 122 and intermetallic layer 124 maybe disposed on transition layer 223. The multi-layer coating 220 of FIG.2 is similar to the multi-layer coating 120 of FIG. 1, except that itadds transition layer 223. The characteristics of diffusion barrierlayer 122 and intermetallic layer 124 are the same as described abovewith respect to FIG. 1 unless otherwise noted. In some embodiments, thetransition layer may include the same components as the diffusionbarrier layer 122 except that transition layer 223 includes agradient-reduced nitrogen. Specifically, there may be a higher molarnitrogen content in the portion of the transition layer 223 closest todiffusion barrier layer 122 and lower or no molar nitrogen content inthe portion of transition layer 223 closest to intermetallic layer 124.For example, the part of transition layer 223 nearest diffusion barrierlayer 122 may be a nitride, such as TiAlN. On the side of transitionlayer 223 closest to intermetallic layer 124, there may be less or nonitrogen present. For example, in the portion nearest intermetalliclayer 124, transition layer 223 may include mostly TiAl, or oxidesthereof, and in the portion nearest diffusion barrier layer 122,transition layer 223 may include mostly TiAlN. In some embodiments, theportion of transition layer 223 in contact with diffusion barrier layer122 may include at least about 20% molar nitrogen content and theportion of transition layer 223 closest to intermetallic layer 124 maynot contain nitrogen. Without being bound by theory, it is believed thattransition layer 223 may reduce the mechanical stress in multi-layercoating 120, especially as compared with a coating which has nitride andnon-nitride layers in direct contact. Since different chemical speciesin the multi-layer coating 120 may have different CTEs, the mechanicalstress between layers of the multi-layer coating 120 may be reduced byforming a layer that utilizes a gradient of a chemical species to reducemechanical stress during heating or cooling. In some embodiments,transition layer 223 may include a molar nitrogen content of greaterthan about 30% at its surface nearest diffusion barrier layer 122 and amolar nitrogen content of less than about 30% at its surface nearestintermetallic layer 124. In another embodiment, transition layer 223 mayinclude a molar nitrogen content of greater than about 35% at itssurface nearest diffusion barrier layer 122 and a molar nitrogen contentof less than about 25% at its surface nearest intermetallic layer 124.In yet another embodiment, transition layer 223 may a molar nitrogencontent of greater than about 40% at its surface nearest the diffusionbarrier layer 116 and a molar nitrogen content of less than about 20% atits surface nearest intermetallic layer 124. In some embodiments, thechange in nitrogen content may change continuously through the thicknessof transition layer 223. In some embodiments, the change in nitrogencontent may change discontinuously through the thickness of transitionlayer 223. It should be understood that transition layer 223 is optionaland that, in some embodiments, the multi-layer coating may be formedwithout the transition layer. In some embodiments, transition layer 223may have a thickness in a range from about 25 nm to about 2,000 nm, fromabout 100 nm to about 800 nm, from about 200 nm to about 500 nm, or fromabout 800 nm to about 1,200 nm.

In some embodiments, as shown for example in FIG. 3, a multi-layercoating 320 may include a TiAl intermetallic layer 335 betweentransition layer 223 and intermetallic layer 124 such that diffusionlayer 122 may be disposed on mold body 110, transition layer 223 may bedisposed on diffusion barrier layer 122, TiAl intermetallic layer 335may be disposed on transition layer 223, and intermetallic layer 124 maybe disposed on TiAl intermetallic layer 335. In some embodiment, TiAlintermetallic layer 335 may include additional metals including, but notlimited to Zr. The multi-layer coating 320 of FIG. 3 is similar to themulti-layer coating 220 of FIG. 2, except that it adds TiAlintermetallic layer 335. The characteristics of diffusion barrier layer112, intermetallic layer 124, and transition layer 223 are the same asdescribed above with respect to FIGS. 1 and 2 unless otherwise noted. Insome embodiments, TiAl intermetallic layer 335 may have a thickness in arange from about 25 nm to about 2,000 nm, from about 100 nm to about 800nm, from about 200 nm to about 500 nm, from about 500 nm to about 2,000nm, or from about 500 nm to about 1,000 nm. In some embodiments, any ofthe multi-layer coatings previously described may have a metal layer 426disposed on intermetallic layer 124. FIG. 4A illustrates a multi-layercoating 420 a similar to multi-layer coating 120 of FIG. 1 except metallayer 426 is disposed on intermetallic layer 124. Similarly, FIG. 4Billustrates a multi-layer coating 420 b similar to multi-layer coating220 of FIG. 2 except metal layer 426 is disposed on intermetallic layer124 and FIG. 4C illustrates a multi-layer coating 420 c similar tomulti-layer coating 320 of FIG. 3 except metal layer 426 is disposed onintermetallic layer 124. In some embodiments, metal layer 426 mayinclude the additional metal of intermetallic layer 124. In someembodiments, refractory metal layer 426 may be included because it maybe less reactive with the glass-based materials that are shaped againstthe mold, and therefore, reduces sticking of the glass-base materials tothe mold during shaping and provides a shaped glass-based material withbetter surface cosmetics. Also, the metal layer 426 may be includedbecause it may make the multi-layer coating more resistant to damagefrom high temperatures (for example, 760° C. to 900° C.), which the moldmay need to withstand when forming glass-based materials havingsoftening points at high temperatures. In some embodiments, metal layer426 may have a thickness in a range from about 25 nm to about 2,000 nm,from about 100 nm to about 800 nm, from about 200 nm to about 500 nm, orfrom about 800 nm to about 1,200 nm.

In some embodiments, any of the multi-layer coatings previouslydescribed may have an oxide layer 528 as the outermost layer of themulti-layer coating. FIG. 5A illustrates a multi-layer coating 520 asimilar to multi-layer coating 120 of FIG. 1 except oxide layer 528 isdisposed on intermetallic layer 124. Similarly, FIG. 5B illustrates amulti-layer coating 520 b similar to multi-layer coating 220 of FIG. 2except oxide layer 528 is disposed on intermetallic layer 124; FIG. 5Cillustrates a multi-layer coating 520 c similar to multi-layer coating320 of FIG. 3 except oxide layer 528 is disposed on intermetallic layer124; FIG. 5D illustrates a multi-layer coating 520 d similar tomulti-layer coating 420 a of FIG. 4A except oxide layer 528 is disposedon metal layer 426; FIG. 5E illustrates a multi-layer coating 520 esimilar to multi-layer coating 420 b of FIG. 4B except oxide layer 528is disposed on metal layer 426; and FIG. 5F illustrates a multi-layercoating 520 f similar to multi-layer coating 420 c of FIG. 4C exceptoxide layer 528 is disposed on metal layer 426. In some embodiments,oxide layer 528 is not a glass former, so the potential for glasssticking to the multi-layer coating is reduced. Also, oxide layer 582may extend the service life of the multi-layer coating thereby improvingthe durability of the multi-layer coating.

In some embodiments, oxide layer 528 may be formed by oxidizing theoutermost layer (e.g., intermetallic layer 124 or metal layer 426) ofthe multi-layer coating using conventional means such as heating. Forexample, in some embodiments, the mold may be heated to a temperature ofat least about 500° C., at least about 600° C., at least about 700° C.,or even at least about 750° C. For example, the coating may be heattreated by heating at a rate of 2° C./min from 20° C. to 750° C.,holding at 750° C. for 30 min, and cooled to room temperature (i.e.,about 25° C.) at furnace rate. As another example, an isothermal processmay be used wherein the coating is oxidized by heat treating at atemperature of 750° C. for about 3 hours without any heat ramping.However, other heat treatments are contemplated herein, including butnot limited to different temperature ramping rates and maximum heatingtemperatures and heating durations. In some embodiments, such as incoating stacks 520 a, 520 b, and 520 c, oxide layer 528 may be an oxidecontaining the titanium, aluminum, and refractory metal fromintermetallic layer 124 when oxide layer 528 is formed by oxidizingintermetallic layer 124. Thus, in some embodiments, oxide layer 528 maybe a TiAlZr oxide In other embodiments, such as in coating stacks 520 d,520 e, and 520 f, oxide layer 528 may be an oxide of the metal of metallayer 426 when oxide layer 528 is formed by oxidizing metal layer 426.Thus, in some embodiments, oxide layer 528 may be zirconium oxide. Insome embodiments, oxide layer 528 may have a thickness in a range fromabout 25 nm to about 2,000 nm, from about 100 nm to about 800 nm, fromabout 200 nm to about 500 nm, or from about 1,000 nm to about 2,000 nm.

In some embodiments, an adhesion layer (not shown) may be disposedbetween mold body 110 and diffusion barrier layer 122. However, in otherembodiments, diffusion barrier layer 122 may be disposed directly onmold body 122 with an intervening layer. The adhesion layer maygenerally be a non-oxidized metal. For example, in embodiments, theadhesion layer may comprise TiAl, Al, Ti, or combinations thereof Theadhesion layer may provide enhanced adhesion between the mold body 110and the diffusion barrier layer 122. Additionally, the adhesion layermay generally smooth the surface of the mold body 110, filling pits andother defects which may interfere with the deposition of at least thediffusion barrier layer 122. It should be understood that the adhesionlayer is optional and that, in some embodiments, the multi-layercoatings may be formed without the adhesion layer.

Generally, a coated mold 100 may be prepared by depositing the variouscoating layers (except for oxide layer 528) onto mold body 110 using adeposition technique, such as physical vapor deposition (PVD). However,other known deposition techniques may be used. In some embodiments, aPVD preparation process may include PVD sputtering of layers of themulti-layer coating (for example with a Cemecon model CC800/9 ML 6(10)coater) at elevated temperatures (for example in a range from 250° C. to650° C. or from 450° C. to 550° C.), high target power (greater than 2kW), and at a substrate bias in a range from 50V to 150V. In someembodiments, when intermetallic layer 124 is a gradient layer there maybe one or more TiAl sputter targets and one or more sputter targets ofthe additional metal (for example, Zr, Ta, Nb, Y, Mo, Hf, andcombinations thereof) and the gradient may be created by adjusting thepower to the appropriate targets to get the desired gradient. In someembodiments, the gradient-reduced nitrogen of transition layer 223 maybe created by reducing the flow rate of nitrogen into the PVD coater,for example by decreasing the rate at a linear rate for about 10minutes.

Following the layer deposition, the coated mold may be heat treated fora time and at a temperature sufficient to oxidize at least a portion ofthe multi-layer coating, such as, for example, heated to a temperatureof at least about 500° C., at least about 600° C., at least about 700°C., or even at least about 750° C. For example, the coating may be heattreated by heating at a rate of 2° C./min from 20° C. to 750° C.,holding at 750° C. for 30 min, and cooled to room temperature (i.e.,about 25° C.) at furnace rate. However, other temperature ramping ratesand maximum heating temperatures are contemplated herein. In oneembodiment, the multi-layer coating is heat treated by exposure toelevated temperatures in a heating device, such as an oven or kiln. Inanother embodiment, the multi-layer coating may be heat treated bydirect exposure to glass at an elevated temperature, such as directcontact with the glass that is being molded. However, any suitableheating process may be performed.

EXAMPLES

The embodiments of the coatings for glass-based-shaping molds describedherein will be further clarified by the following examples. The examplesare illustrative in nature, and should not be understood to limit thesubject matter of the present disclosure.

Example 1

A multi-layer coating was deposited on a mold substrate of Inconel 600using a PVD coater available from Cemecon (Model No. CC800/9 ML 6(10)).Three TiAl sputter targets with a Ti/Al ratio of 1 and a power of 5 kWand 1 sputter target of pure zirconium with a power of 2.5 kW were used.The heater power was 2 kW and the chamber pressure was 550 mPa. Firstpower was supplied only to the TiAl sputter targets for about 32 minutesin a nitrogen atmosphere to form a TiAlN layer. Then the flow rate ofnitrogen was decreased at a linear rate to zero for about 10 minutes tocreate a transition layer with a gradient-reduced nitrogen content.During the last 30 seconds of the nitrogen ramp down, power to the Zrsputter target was ramped up to 0.5 kW. Then the power to the Zr sputtertarget was increased at a linear rate for about 3 minutes to a power of2.5 kW to form a TiAlZr intermetallic layer. FIG. 6 is a plot of theassumed concentration in atomic weight % based on targeted values vs.the depth of the mold with the multi-layer coating for each element (Ni,Cr, Fe, Mn, Si, Cu, c, Si, N, Ti, Al, Zr). The data from FIG. 6 is basedon the as deposited layers prior to oxidizing the outermost layer andshows that (1) the diffusion barrier layer blocks diffusion of themetals from the base mold into the top layers of the multi-layer coatingand (2) that the composition of the top layers of the multi-layercoating are deposited as described.

Example 2

0.7 mm thick sheets of Corning glass code 2320 were molded to have abend radius of 9 mm using a nickel 201 mold and a coated Inconel 600mold of Example 1. The nickel 201 mold had an outer layer of nickeloxide that was approximately 4 to 7 μm thick. The coated Inconel mold ofExample 1 had an additional outermost oxide layer that was approximately1 to 1.5 μm thick.

The glass sheets shaped on the nickel 201 mold were placed on the moldand heat and vacuum were applied according to the profile shown in FIG.9. The glass sheets shaped on the Inconel 600 mold were placed on themold and heat and vacuum were applied according to the profile shown inFIG. 9.

After the glass sheets were molded, the peak to valley depth of theimprints of any pits on the surface of the molded glass sheets weremeasured using a Zygo optical profilometer. The peak to valley depthswere averaged for the sheets molded on the nickel 201 mold and thesheets molded on the Inconel 600 mold. The peak mold temperature wastemperature was 750° C. for both the nickel 201 and the Inconel 600molds As can be seen in FIG. 10, the roughness of the glass sheet shapedusing the nickel 201 mold is significantly higher than the glass sheetsshaped using the coated Inconel 600 mold. Accordingly, the multi-layercoatings described herein minimize the imprints imparted on glass-basedmaterial from the mold as measured by the peak to valley depth ofimprints formed in the shaped glass-based material. As a result,glass-based material shaped with molds having the multi-layer coatingsdescribed herein require less polishing to remove the imprints.

It should now be understood that the coatings disclosed herein may offerthe advantage of reduced stickiness between the mold and the glass-basedmaterial, thus reducing or wholly eliminating cosmetic defects in moldedglass-based material, such as stains, pitting, and scuffing. Thecoatings described herein may also have enhanced durability, and mayallow for extending mold life to at least 2,000 cycles before thecoating must be stripped and reapplied to the mold.

It is noted that the terms “substantially” and “about” may be utilizedherein to represent the inherent degree of uncertainty that may beattributed to any quantitative comparison, value, measurement, or otherrepresentation. These terms are also utilized herein to represent thedegree by which a quantitative representation may vary from a statedreference without resulting in a change in the basic function of thesubject matter at issue.

Various modifications and variations can be made to the embodimentsdescribed herein without departing from the scope of the claimed subjectmatter. Thus it is intended that the specification cover themodifications and variations of the various embodiments described hereinprovided such modification and variations come within the scope of theappended claims and their equivalents.

We claim:
 1. A mold comprising: a mold body having an outer surface anda multi-layer coating disposed on the outer surface, wherein themulti-layer coating comprises: a diffusion barrier layer disposed on theouter surface of the mold body; and an intermetallic layer disposed onthe diffusion barrier layer, wherein the intermetallic layer comprisesTi, Al, and an additional metal selected from the group consisting ofZr, Ta, Nb, Y, Mo, Hf, and combinations thereof, and wherein thediffusion barrier layer restricts diffusion of metal from the mold bodyto the intermetallic layer.
 2. The mold of claim 1, further comprising atransition layer disposed between the diffusion barrier layer and theintermetallic layer, wherein the transition layer comprises a change innitrogen content with a higher molar nitrogen content in a portion ofthe transition layer closest to the diffusion barrier layer and a lowermolar nitrogen content in a portion of the transition layer closest tothe intermetallic layer.
 3. The mold of claim 1, wherein theintermetallic layer comprises a change in the additional metal contentwith a lower molar content of the additional metal in a portion of theintermetallic layer closest to the diffusion barrier layer and a highermolar content of the additional metal in a portion of the intermetalliclayer farthest from the diffusion barrier layer.
 4. The mold of claim 1,further comprising an oxidized intermetallic layer disposed on theintermetallic layer.
 5. The mold of claim 1, wherein the ratio oftitanium molar content to aluminum molar content in the multi-layercoating is in a range from about 0.67 to about
 1. 6. The mold of claim5, wherein the ratio of titanium molar content to aluminum molar contentin the multi-layer coating is about
 1. 7. The mold of claim 5, whereinthe ratio of titanium molar content to aluminum molar content in themulti-layer coating is greater than or equal to about 0.67 and less thanabout
 1. 8. The mold of claim 1, wherein a sum of the molarconcentration of titanium and aluminum in the intermetallic layer isgreater than or equal to the molar concentration of the additional metalin the intermetallic layer.
 9. The mold of claim 1, wherein a sum of themolar concentration of titanium and aluminum in the intermetallic layeris less than the molar concentration of the additional metal in theintermetallic layer.
 10. The mold of claim 1, further comprising a metallayer comprising the additional metal of the intermetallic layerdisposed on the intermetallic layer.
 11. The mold of claim 10, whereinthe intermetallic layer comprises a change in additional metal contentwith a lower molar content of the additional metal in a portion of theintermetallic layer closest to the diffusion barrier layer and a highermolar content of the additional metal in a portion of the intermetalliclayer closest to the metal layer.
 12. The mold of claim 10, furthercomprising an oxidized metal layer disposed on the metal layer.
 13. Themold of claim 1, wherein the additional metal is zirconium.
 14. The moldof claim 1, wherein the mold body is predominantly a metal selected fromthe group consisting of iron, nickel, chromium, copper, mixturesthereof, and alloys thereof.